We are studying the effects of individual dietary components and interactions of components on lipid metabolism and atherosclerosis. Using cholesterol containing diets we are assessing the effects of randomized butter, lard, peanut oil and corn oil on the progression and regression of atherosclerosis in rabbits. Other experiments will involve semi-purified, cholesterol-free diets in which protein and fiber will be varied. These diets will also be fed to rats in order to determine their effects on enzymes of cholesterol metabolism such as liver cholesterol 7 alpha-hydroxylase and HMG-CoA reductase. Other studies will include investigation into the influence of type and amount of non-nutritive fiber on cholesterol synthesis, absorption and degradation. The overall aim is the delineation of the role of dietary interactions in determining cholesterol and bile acid metabolism and severity of atherosclerosis.